The present invention relates generally to axial retention and anti-rotation of annular members mounted to turbine rotors and, more particularly, to keys to prevent rotation of forward outer seals mounted to a turbine disk.
Some turbine aircraft engines, particularly of the high bypass ratio type, includes multi-stage high pressure compressor and turbine sections interconnected by a central compression shaft or, in some models, a forward shaft. The high pressure turbine section typically includes first and second stage disks in which the second stage disk is attached to the first stage disk by a bolted connection. Forward and aft face plates attached to forward and aft faces of the first stage disk provides axial retention of first stage turbine blades radially retained in axially extending slots in a rim of the first stage disk. The forward face plate also helps define a cooling airflow path to the slots and has a forward outer seal mounted to it.
Bolted connections were used between components. Disadvantages of such bolted connections include bolt holes in the disks which create stress concentrations and limit the useful lives of the seals and disks. Furthermore, additional disk weight is required to sustain the stresses imposed by the bolt and bolt hole engagements. Another disadvantage with such bolted connections is that alignment of the first and second stage disks and seals is difficult to maintain during assembly and operation, which may result in excessive vibrations during operation. To overcome these and other disadvantages, boltless connections were developed, thereby eliminating the time-consuming task of properly torquing the bolts and eliminating the stress concentration problems associated with bolted connections.
Bayonet connections have been developed for preventing relative axial movement between the face plates and disks. Some of these boltless connections further provided anti-rotation features for preventing rotation of the members such as the face plates with respect to the first stage disk. These features included anti-rotation keys and axial retaining wires or rings. See U.S. Pat. No. 5,320,488, by Meade, et al., issued Jun. 14, 1994, and is entitled “Turbine Disk Interstage Seal Anti-rotation System” and U.S. Pat. No. 5,236,302, by Weisgerber, et al., issued Aug. 17, 1993, and is entitled “Turbine Disk Interstage Seal System”, and U.S. Pat. No. 5,318,405, by Meade, et al., issued Jun. 7, 1994, and is entitled “Turbine Disk Interstage Seal Anti-rotation Key Through Disk Dovetail Slot”.
U.S. Pat. No. 5,275,534, by Cameron, et al., issued Jan. 4, 1994, and is entitled “Turbine disk forward seal assembly”. U.S. Pat. No. 5,275,534 discloses a turbine section having a disk and a forward seal assembly including a face plate. The face plate includes a plurality of radially inwardly-extending tabs shaped to engage radially outwardly-extending tabs located on the web to form a bayonet connection. Locking pins are arranged to balance the assembly. Relative circumferential movement is prevented by locking pins, secured by a split ring, in between the tabs of the bayonet engagement or alternatively a locking cylinder instead of the locking pins.
Some anti-rotation systems include a key positioned in at least one slot in the plate and a tab for interconnecting with a slot formed in the bayonet connection. The key prevents relative circumferential movement and a seal plate is provided for retaining the key in the interconnected position between the face plate and the disk.
The retaining rings and seal plates have significant amounts of weight. The anti-rotation keys have complicated designs and are not easy to manufacture. Different engines across an engine line often need retaining rings and seal plates with different sizes and shapes which adds cost to the manufacture and servicing and repair of the engine. It is desirable to make the turbine design less costly to manufacture and service, to make it lighter in weight, and more simple to manufacture and service.